Edit: Duplicate, cannot delete myself.
I had the same issue, my windows were resizing and their heights were getting 100-200 px.
I have applied all the suggested Group Policy settings here and from other similar issues, but none of them helped.
Then during my repeated reconnect tests, I have noticed that the windows are shown as normal for a moment and then getting resized.
In my case, I had configured a non-standard resolution (by editing the rdp file), 1750x1050 which fits well for my needs. I thought that might be the case and changed it to a standard 1680x1050, and my issues were gone. Thus, try using a standard resolution (The one you select from the Remote Desktop connect window). I hope this resolves your problem as well.